The technique disclosed herein relates to a physical quantity detection circuit used for a physical quantity sensor that detects a physical quantity given externally and to a physical quantity sensor device provided with the same, and more particularly, to a technique of adjusting the phase relationship between a sensor signal and a detection signal.
Conventionally, physical quantity sensor devices capable of detecting a physical quantity (e.g., an angular velocity, an acceleration, etc.) are used in a variety of technical fields such as detection of shake of a digital camera, attitude control of a mobile unit (e.g., an aircraft, an automobile, a robot, a vessel, etc.), and guidance of a missile and a spacecraft. In general, a physical quantity sensor device includes: a physical quantity sensor that outputs a sensor signal according to a physical quantity given externally; and a physical quantity detection circuit that detects a physical quantity signal (signal corresponding to the physical quantity) from the sensor signal using a detection signal (signal having a frequency corresponding to the frequency of the sensor signal).
In recent years, with the progress of the circuit nanotechnology, more and more physical quantity detection circuits are being implemented using digital circuits. Japanese Patent Gazette No. 2728300 (Patent Document 1) discloses a signal processing circuit for a biaxial angular velocity/acceleration sensor, which is composed of digital circuits. In this signal processing circuit, while an analog-to-digital converter circuit converts a sensor signal from the sensor to a digital sensor signal, a sine wave signal generation circuit generates a digital sine wave signal, and a digital multiplier circuit multiplies the digital sensor signal by the digital sine wave signal. For example, as shown in FIG. 17, the analog-to-digital converter circuit samples a sensor signal in synchronization with a sampling clock (i.e., every sampling period) and converts sampled analog values (amplitude values) A0, A1, A2, . . . of the sensor signal to digital values P0, P1, P2, . . . .
In a physical quantity detection circuit, whether it is an analog circuit or a digital circuit, it is important to adjust the phase relationship between a sensor signal and a detection signal so that these signals can be synchronous with each other. Such a phase adjustment technique is disclosed in Japanese Laid-Open Patent Publication No. 8-14916 (Patent Document 2). A vibration gyro disclosed in Patent Document 2 is provided with a phase correction circuit including a temperature-sensitive element (element having a predetermined temperature characteristic), to correct a phase shift of the detection signal caused by a temperature change.